Mercury bioaccumulation in arthropods from typical community habitats in a zinc-smelting area

This study assessed the enrichment of mercury in the food web from the different community habitats in a zinc-smelting area of China. We used a nitrogen stable isotope technique to analyze trophic level relationships among arthropods and found that the first trophic level consisted of plants in the different community habitats, the second trophic level consisted of herbivores such as locusts and grasshoppers (primary consumers), and the third trophic level included spiders and mantes (secondary consumers). Mercury enrichment in the primary consumers was not evident, but enrichment in arthropods of the third trophic level was significant. The average of enrichment coefficients in spiders and mantes was greater than 1. The δ¹⁵N values indicated that mercury concentrations accumulated from primary producers to top carnivorous arthropods increased. In this zinc-smelting area, the biological amplification of mercury in the food web is significant. It is reasonable to assume that humans, located at the top of the food chain, are exposed to biomagnified levels of mercury.     

Hydrodynamics and contaminant transport on a degraded bed at a 90-degree channel confluence

Channel confluences at which two channels merge have an important effect on momentum exchange and contaminant diffusion in both natural rivers and artificial canals. In this study, a three-dimensional numerical model, which is based on the Reynolds Averaged Navier–Stokes equations and Reynolds Stress Turbulence model, is applied to simulate and compare flow patterns and contaminant transport processes for different bed morphologies. The results clearly show that the distribution of contaminant concentrations is mainly controlled by the shear layer and two counter-rotating helical cells, which in turn are affected by the discharge ratio and the bed morphology. As the discharge ratio increases, the shear flow moves to the outer bank and the counter-clockwise tributary helical cell caused by flow deflection is enlarged, leading the mixing happens near the outer bank and the mixing layer distorted. The bed morphology can induce shrinkage of the separation zone and increase of the clockwise main channel helical cell, which is initiated by the interaction between the tributary helical cell and the main channel flow and strengthened by the deep scour hole. The bed morphology can also affect the distortion direction of the mixing layer. Both a large discharge ratio and the bed morphology could lead to an increase in mixing intensity.     

气-固耦合作用下煤层气注热开采热量迁移规律数值模拟

为获取气固耦合作用下煤层气注热开采过程热量分布规律,探究煤层内气-固体系吸热量的影响因素,采用自行研制的三轴煤层气解吸热量测试验装置,在实验室中对柱状原煤进行了不同轴、围压条件下煤体甲烷解吸过程温度及热量变化测定,利用温度补偿原理获取了解吸热与解吸量关系理论模型,利用COMSOL Multiphysics软件进行了煤层气注热开采过程热量迁移规律数值模拟.结果表明:解吸热随解吸量呈指数增长趋势;模拟结果显示井间距为60 m时相较于40 m时煤层吸热量更快达到稳定,吸附气体吸热量升高持续时间为井间距40 m时的1.9倍;解吸热量在注热温度为593 K时较注热温度为493 K时增加15.97％,且达到最终解吸热量稳定时间减少21.4％.对比分析得到,在单井注热开采条件下,增大井间距和提高注热温度均可以不同程度影响热量在煤层中迁移、增大解吸热量并促进解吸作用,进而大幅度提升煤层气井筒累计产量.研究结果可为低渗透储层煤层气高效安全开采及煤层气注热开采工艺方案优化提供理论支撑.     

Nationwide survey on the natural radionuclides in industrial raw minerals in South Korea

A Nationwide survey on the natural radioactivity in industrial raw mineral commodities (17 kinds of domestic and 18 kinds of imported) that are representative minerals used in production and consumption in South Korea was conducted. The target industrial minerals can be categorized into two groups. The first group covers non-metallic and metallic raw minerals with low levels of radioactivity such as clay, silica sand, carbonates, bituminous and anthracite coal, iron ores, ilmenite, rutile, and phosphate ore. The other group comprises minerals with high levels of radioactivity including zircon and monazite. One hundred and sixty-four domestic and imported samples were analysed by gamma-ray spectroscopy using an HPGe detector. The (40)K content ranges from <0.00131 to 2.69Bq g(-1), and (226)Ra and (232)Th range over <0.0006 to 0.630 and <0.0008 to 0.474Bq g(-1), respectively. There was no anthropogenic radioactive signal in any of the samples.     

Improvement of nuclide leaching resistance of paraffin waste form with low density polyethylene

Low-level liquid borate wastes have been immobilized with paraffin wax using a concentrate waste drying system (CWDS) in Korean nuclear power plants. The possibility for improving chemical durability of paraffin waste form was suggested in this study. A small amount of low density polyethylene (LDPE) was added to increase the leaching resistance of the existing paraffin waste form. The influence of LDPE on the leaching behavior of waste form was investigated by performing leaching test according to ANSI/ANS-16.1 procedure during 325 days. It was observed that the leaching of nuclides immobilized within paraffin waste form made a marked reduction although little content of LDPE was added to waste form. The acceptance criteria of paraffin waste form associated with leachability index (LI) and compressive strength after the leaching test were fully satisfied with the help of LDPE.     

Numerical Simulation of Light/Dark Cycle Frequency of Microalgae Fluid in a Helical Tubular Photobioreactor for Carbon Dioxide Capture

In the present study, three-dimensional numerical simulations are conducted on hydrodynamics and light-intensity distribution of microalgae fluid flow in a helical tubular photobioreactor for CO₂ capture. The effect of incident direction of the light illumination is discussed and the light/dark cycle frequency experienced by the microalgae fluid in the cross-section of the photobioreactor is investigated. The simulation results reveal the steadily nonhorizontal and unsymmetrical Dean roll-cells of the microalgae fluid flow in the cross-section of the helical tube. The external light projecting onto the helical tubular photobioreactor from the center is a better way for microalgae cultivation. The light/dark cycle frequency of the microalgae fluid flow is calculated based on the light-intensity distribution inside the photobioreactor. The light/dark cycle frequency keeps constant for the same stream trace of the microalgae flow while varies with different flow regions. Meanwhile, the light/dark cycle frequency increases with the increase in microalgae fluid velocity. The suitable demarcation between the light and the dark zone depends on the shape and the location of the Dean roll-cells.     

Near-surface wind profile test based on accuracy verification of UAV anemometer lifting height in an urban fringe built-up area

Environmental Science and Pollution Research - Multirotor UAVs (unmanned aerial vehicles) have been widely used in urban vertical wind environment testing, whereas less attention has been given to...     

不同处理方法去除有机质对沉积物吸附有机农药和非离子表面活性剂的影响

四种不同的方法去除沉积物有机质,采用振荡平衡法研究了有机农药、非离子表面活性剂在沉积物上的吸附行为及非离子表面活性剂对有机农药吸附的影响.结果表明,经HCl处理后,沉积物有机碳含量增加,而经Na4 P2O7,NaOH和H2O2处理后沉积物有机碳含量均降低;甲基对硫磷、西维因的吸附取决于沉积物有机碳的分配作用,与矿物质无关;沉积物矿物组分的表面作用和微孔性作用使得高极性有机农药克百威在低有机碳含量沉积物七的吸附量增加;Tween-80使甲基对硫磷在未处理和HCl处理的沉积物上的吸附量减少,在NaOH处理和H2O2处理的沉积物上的吸附量增加.